Polyphenyl thioether lubricating compositions

ABSTRACT

Lubricating compositions comprising polyphenyl thioethers, polyphenyl ethers-thioethers or mixtures thereof and containing small amounts of an organic phosphinic acid have improved lubricating properties. These compositions are useful as lubricants over wide temperature ranges.

Umted States Patent 1 11 1 3,718,590

Clark 1 51 Feb. 27, 1973 54 POLYPHENYL THIOETHER 2,957,931 10/1960 Hamilton et a1 ..252/49.s x LUBRICATING COMPOSITIONS 3,426,075 2/1969 Campbell ..252/45 [75] Inventor: Frank S. Clark, St. Louis, Mo. FOREIGN PATENTS OR APPLICATIONS [7 3] Assignee: Monsanto Company, St. Louis, Mo. 5 5 10/1960 Great Britain [22] Filed: Dec. 28, 1970 Primary ExammerDan1el E. Wyman PP 102,152 Assistant Examiner--W. Cannon A!torney--Neal E. Willis, J. E. Maurer and William T. 52 us. (:1. ..252/46.7, 252/466, 252/49.8, Black 260/5024 R 51 1111.01. ..Cl0n1 1/48 [571 ABSTRACT of Search "252/45, 48.4, 46-6, compositions comprising thioethers, polyphenyl ethers-thioethers or mixtures [56] References C'ted thereof and containing small amounts of an organic UNITED STATES PATENTS phosphinic aci clhave improved lubricating properties. These composltions are useful as lubrlcants over w1de 2,174,019 9/1939 Sullivan ..252/49.8 temperature ranges. 2,274,291 2/1942 Clayton et a1. 2,730,499 1/1956 Pokomy ..252/49.8 5 Claims, N0 Drawings POLYPHENYL THIOETHER LUBRICATING COMPOSITIONS This invention relates to improved lubricating compositions comprising polyphenyl thioethers, mixed polyphenyl estersthioethers and mixtures thereof, containing from three to eight aromatic groups and a small amount of an organic phosphinic acid as a lubricating additive.

Polyphenyl thioethers and polyphenyl etherthioether combinations have found wide application as functional fluids due to their excellent thermal stability and lubricity. For example they have been found to be valuable as hydraulic fluids and as lubricants in motor operation, particularly in jet engines.

Development of synthetic base stocks such as the polyphenyl thioether has provided lubricant fluids which are useful at elevated temperature such as 400 to 500 F. It is known that one of the aspects in which the polyphenyl thioether base stocks are considered deficient is in their lubricating characteristics, especially for steel on steel, steel on silvered bronze, or steel on cast iron. These lubricating characteristics include the load-carrying abilities and wear properties. Thus there is a demand for additives for polyphenyl thioethers which will improve the lubricity of the polyphenyl thioethers for steel on the above metallur- E)- An object of the present invention is to provide for improved lubricating compositions employing polyphenyl thioethers, polyphenyl ether-thioethers, or mixtures thereof as base stocks.

These and other objects will become evident upon consideration of the following specification and examples.

It has now been found that compositions consisting essentially of a major amount of a polyphenyl thioether base fluid having the formula wherein R is a phenyl group, an alkyl-substituted phenyl group wherein the alkyl group contains one to four carbon atoms, an alkoxy-substituted phenyl group wherein the alkoxy group contains one to four carbon atoms or a halogenated phenyl group wherein the halogen is bromine, fluorine or chlorine, R is a phenylene group, an alkyl or alkoxy-substituted phenylene group where the alkyl group contains one to four carbon atoms or a halogenated phenylene group wherein the halogen is fluorine, bromine or chlorine, and Y is selected from oxygen and sulfur but at least one of the Ys is sulfur and n is an integer having a value of from one to six and an additive amount of an aryl phosphinic acid have unusual ability to lubricate steel on cast iron, silver plated bronze, or steel.

The amount of the organic phosphinic acid employed in the compositions of this invention is from about 0.05 to about 2.0 percent by weight of the total composition. It is preferred to employ the aryl phosphinic acid in the compositions of this invention in amounts of from about 0.075 to about 0.2 percent by weight of the total composition.

The improvement in lubricity characteristics achieved by the addition of the aryl phosphinic acid to the polyphenyl thioether base fluid is unusual and surprising. Wear on a silver plated bronze bearing surface R1|OH H wherein R" is an aryl group containing from six to 16 carbon atoms, halogen substituted aryl groups or an alkyl group containing one to 12 carbon atoms or halogen substituted alkyl groups. Illustrative of the groups represented by R" are, for exaMple, phenyl, tolyl, xylyl, naphthyl, a-methyl naphthyl and diphenyl, and aryl groups substituted with halogen or with alkyl groups containing from one to 10 carbon atoms. Such alkyl substituted aryl groups are tolyl, xylyl, a-methyl naphthyl, nonylphenyl, ethylphenyl, butylphenyl, t-butylphenyl and the like. Such halogen substituted aryl groups are o-, mand p-chlorophenyl, o-, mand pbromophenyl, the fluorophenyl groups and the like. [1- lustrative of the alkyl groups represented by R" are, for example, methyl, ethyl, propyl, isopropyl, butyl, t-butyl, hexyl, isooctyl, decyl, dodecyl and the like. Such organic phosphinic acids are, for example, phenyl phosphinic acid, nonylphenyl phosphinic acid, tolyl phosphinic acid, xylyl phosphinic acid, naphthyl phosphinic acid, diphenyl phosphinic acid and the like. It is particularly preferred to employ in the compositions of this invention organic phosphinic acids wherein R" is an aryl group within the above-defined definition.

The polyphenyl thioethers employed in the composition of this invention have from three to eight benzene rings and from one to seven sulfur atom with the sulfur atoms joining the benzene rings in chains as ether linkages.

By the term polyphenyl thioether as used herein is meant a compound or physical mixture of compounds represented by Formula I. The term includes compounds wherein all of the Ys in Formula I are sulfur. The term also includes those compounds which contain both oxygen and sulfur linkages between the benzene rings.

The compositions of this invention contain a major amount of the polyphenyl thioether base stock, i.e., at least 50 percent by weight of the total composition comprises a polyphenyl thioether. It is preferred that at least 60 percent by weight of the composition be a polyphenyl thioether base stock and even more preferred that at least 85 percent by weight of the total composition comprise a polyphenyl thioether.

The compositions of this invention can also contain from 0.01 to 10 percent by weight of the total composi- Illustrative of the alkyl-substituents present in the phenyl and phenylene groups of the polyphenyl thioethers are for example, methyl, ethyl, propyl, butyl and the like. Illustrative of the alkoxy-substituents are, for example, methoxy, ethoxy, propoxy, butoxy, and their isomers.

Illustrative of the polyphenyl thioethers which can be employed as base stocks for the compositions of this invention are the bis(phenylmercapto)benzenes. For example bis(m-phenylmercapto )benzene bis(o-phenylmercapto)benzene bis(p-phenylmercapto)benzene bis(m-phenylmercaptophenyl)sulfide bis(o-phenylmercaptophenyl)sulfide bis(p-phenylmercaptophenyl)sulfide (m-phenylmercaptophenyl) (o-phenylmercaptophenyl)sulfide p-phenylmercapto-m-phenylmercapto diphenyl sulfide o-bis(o-phenylmercaptophenylmercapto)benzene p-bis(p-phenylmercaptophenylmercapto)benzene p-bis(o-phenylmercaptophenylmercapto)benzene p-bis(m-phenylmercaptophenylmercapto )benzene m-bis(p-phenylmercaptophenylmercapto)benzene o-bis(p-phenylmercaptophenylmercapto)benzene and the like and mixtures thereof.

Illustrative of the mixed polyphenyl ether-thioether compounds which can be employed as base stocks in the compositions of this invention are for example,

o-phenylmercapto-m-phenoxy benzene p-phenylmercapto-o-phenoxy benzene m-phenoxy-p-phenylmercapto benzene o-phenylmercapto-p'-phenoxydiphenyl sulfide o-phenylmercapto-m'-phenoxydiphenyl sulfide o-phenoxy-m'-phenylmercaptodiphenyl sulfide m-phenoxy-p'-phenylmercaptodiphenyl sulfide o-phenoxy-p-phenylmercaptodiphenyl sulfide p-phenoxy-p-phenylmercaptodiphenyl sulfide o-phenoxy-o'-phenylmercapt0diphenyl sulfide o,o-bis( phenylmercapto)diphenyl ether o-phenylmercapto-m-phenylmercaptodiphenyl ether o-phenylmercapto-p-phenylmercaptodiphenyl e ther m-(m-phenylmercaptophenylmercapto) (m-phenoxyphenyl-mercapto)benzene [m- (m-phenylmercaptophenylmercapto)phenyl] [m-(m-phenoxyphenylmercapto)phenyl] sulfide 3-(m-phenylmercaptophenylmercapto)-3-(m-phenyl-mercaptophenoxy )diphenyl sulfide 3,3-bis(m-phenylmercaptophenylmercapto)diphen yl ether 3-(m-phenylmercaptophenylmercapto)-3-(mphenoxyphenoxy)diphenyl sulfide 4-(m-phenylmercaptophenylmercapto)-4'-(m-phenylmercaptophenoxy)diphenyl ether 3-(m-phenylmercaptophenylmercapto)-3-(mphenoxyphenylmercapto)diphenyl ether 4,4-bis(m-phenylmercaptophenoxy)diphenyl sulfide 4,4-bis(m-phenoxyphenylmercapto)diphenyl sul- 3-( m-phenoxyphenylmercapto )-3 -(m-phenylmercaptophenoxy)diphenyl sulfide 3 ,3 '-bis( m-phenylmercaptophenoxy)diphenyl ether 4-(m-phenylmercaptophenylmercapto-4'-(mphenoxyphenoxy)diphenyl ether 3-(p-phenylmercaptophenoxy )-3 -(p-phenoxyphenoxy)diphenyl sulfide 3-(m-phenylmercaptophenoxy)-3-(m-phenoxyphenylmercapto)dipenyl ether 3,3'-bis(m-phenoxyphenylmercapto)diphenyl ether and 3-( m-phenoxyphenylmercapto )-3 m-phenoxyphenoxy)diphenyl sulfide.

In addition to the foregoing compounds, the phenyl and phenylene groups of such compounds can contain substituents, such as alkyl of one to four carbon atoms, alkoxy of one to four carbon atoms and halogen such as chlorine, bromine and fluorine. Examples of such compounds are as follows:

4,4-bis(m-tolylmercapto)diphenyl ether 3 ,3 '-bis( m-tolylmercapto )diphenyl ether 2,4'-bis(m-tolylmercapto)diphenyl ether 3 ,4-bis(m-tolylmercapto)diphenyl ether 3 ,3 '-bis(p-tolylmercapto )diphenyl ether 3,3-bis(xylylmercapto)diphenyl ether 4,4'-bis(xylylmercapto)diphenyl ether 3,4'-bis(xylylmercapto )diphenyl ether 3,4'-bis(m-isopropylphenylmercapto)diphenyl ether 3,3-bis(m-isopropylphenylmercapto)diphenyl ether 2,4'-bis(m-isopropylphenylmercapto )diphenyl ether 3,4'-bis(p-tert-butylphenylmercapto)diphenyl ether 4,4-bis(p-tert-butylphenylmercapto)diphenyl ether 3,3bis(p-tert-butylphenylmercapto)diphenyl ether 3,3-bis(2,4-di-tert-butylphenylmercapto )diphenyl ether 3,3-bis(3-chlorophenylmercapto)diphenyl ether 4,4'-bis( 3-chlorophenylmercapto)diphenyl ether 3,3 '-bis(m-trifiuoromethylphenylmercapto)diphenyl ether 4,4'-bis(m-trifluoromethylphenylmercapt0)diphenyl ether 3,4-bis(m-trifiuoromethylphenylmercapto)diphenyl ether 2,3'-bis(m-trifluoromethylphenylmercapto)diphenyl ether 3,3-bis(p-trifluoromethylphenylmercapto)diphenyl ether 3,3'-bis(o-trifiuoromethylphenylmercapto )diphenyl ether 3 ,3 '-bis(m-methoxyphenylmercapto )diphenyl ether 3,4-bis(m-isopropoxyphenylmercapto)diphenyl ether 3,4-bis(m-perfluorobutylphenylmercapto )diphenyl ether 2-(m-tolyloxy)-2-phenylmercaptodiphenyl sulfide 2-(p-tolyloxy)-3'-phenylmercaptodiphenyl sulfide 2-(o-tolyl0xy)-4-phenylmercaptodiphenyl sulfide 3-(m-tolyloxy)-3-phenylmercaptodiphenyl sulfide 3-( m-tolyloxy)-4-phenylmercaptodiphenyl sulfide 4-( m-tolyloxy)-4'-phenylmercaptodiphenyl sulfide 3-xylyloxy-4-phenylmercaptodiphenyl sulfide 3-xylyloxy-3 -phenylmercaptodiphenyl sulfide 3-phenoxy-3'-(m-tolylmercapto)diphenyl sulfide 3-phenoxy-4'-(m-tolylmercapto)diphenyl sulfide 2-phenoxy-3-(p-tolylmercapto)diphenyl sulfide 3-phenoxy-4-(m-isopropylphenylmercapto)diphenyl sulfide 3-phenoxy-3-(m-isopropylphenylmercapto)diphenyl sulfide 3-m-toloxy-3-(m-isopropylphenylmercapto)diphenyl sulfide 4-(m-trifluoromethylphenoxy )-4-phenylmercaptodiphenyl sulfide 3-(m-trifluoromethylphenoxy)-4-phenylmercaptodiphenyl sulfide 2-(m-trifluoromethylphenoxy )-3'-phenylmercaptodiphenyl sulfide 3-(m-trifluoromethylphenoxy)-3'-phenylmercaptodiphenyl sulfide 3-(p-chlorophenoxy )-3 '-phenylmercaptodiphenyl sulfide 3-(m-bromophenoxy)-4-phenylmercaptodiphenyl sulfide bis[m-(m-chlorophenoxy )phenyl]sulfide m-bis[3-(p-methylphenylmercapto)phenoxy ]benzene m-bis[3-(m-trifluoromethylphenoxy )phenylmercap to]benzene m-bis[3-(m-bromophenoxy)phenylmercapto ]benzene 3 ,3 '-bis[ m-( p-methylphenylmercapto )phenoxy] diphenyl sulfide 3,4-bis[m-(p-methylphenylmercapto )phenoxy] diphenyl sulfide 3-(p-xenyloxy)-3 '-phenylmercapto diphenyl sulfide, and the like and mixtures thereof. It is also contemplated within the scope of this invention to employ mixtures of polyphenyl ether-thioethers as base stocks.

The compositions of this invention are useful as lubricants under extreme conditions. The compositions are especially useful for lubrication of steel on steel, silvered bronze, cast iron and the like.

EXAMPLE 1 meta-bis(phenylmercapto)benzene bis(phenoxyphenyl )sulfide (phenoxyphenyl) (phenylmercapto phenyl)sulfide (50% by weight) 12.5% by weight) (23.5% by weight) bis(phenylmercaptophenyl)sulfide 12.65% by weight) 3 ring and 5 ring thioethers (l.35% by weight) and containing parts per million of a dimethyl silicone antifoam agent (Dow-Corning 200, 350 cs. fluid).

The mixture was tested for lubricity on a high temperature wear machine. This machine comprises a steel shaft rotating on a silvered bronze disc so that there is line contact between the shaft and the disc. This test simulates the cage wear of silver plated bronze bearing cages. A lever movable about an axis permits the test disc to be loaded against the test shaft. The heated steel shaft (640 F.) is rotated against the disc at 30,180 rpms at a load of 2.25 dekanewtons while the contacting surfaces are lubricated with the test oil at a flow rate of 1 ml. per minute. In the test the shaft requires 1 minute rotation to reach speed (30,180 rpm) and is maintained at this speed for 5 minutes and is then allowed to coast to a stop (1 minute). The wear scar is then measured. A test failure is indicated by seizure of the shaft and disc or an excessive wear scar.

When the mixture of Example 1 was tested at 640F., the shaft did not seize and the scar wear was not excessave.

When the base fluid without the phenyl phosphinic acid was tested at 640 F. it failed the test.

The lubricating ability of the fluid from Example 1 was also shown with a slow speed four ball machine. A slow speed four ball machine measures the boundry lubricity action of additives. This test is a variation of the well known Shell Four Ball Test in which a ball is rotated against three stationary balls. Wear scars and/or seizure loads measure additive lubricity. In the slow speed instrument the three stationary balls are replaced with circular discs. Standard operating conditions are:

3 Kg. Load 1 rpm.

Room temperature to 700 F.

The speed of rotation is very low, namely one r.p.m. This equals 0.88 inches/minute. This is done for two reasons. It insures boundary conditions, i.e., metal to metal contact. It also eliminates metal skin temperature flashes which can occur at high speeds. Thus the bulk oil temperature is equivalent to the metal surface temperature. Under these conditions wear is negligible and friction is used to follow lubrication. After covering the ball and disc with the test oil, the initial friction is recorded. The test sample is then heated to 700 F. with continuous recording of the friction. This gives a boundary friction-temperature profile for the experimental fluid over this temperature range.

The mixture of Example 1 was tested by this procedure on 316 stainless steel. The coefficient of friction observed was always between 0.30 and 0.66 from room temperature to 700 F.

When the base fluid without the phenyl phosphinic acid was tested under the same conditions the coefficient of friction showed a steep increase as the temperature was increased and exceeded 2.0.

The lubricating ability of the composition of Example 1 was also shown by a high speedFalex Test employing an M-lO steel pin and Meehanite cast iron blocks. The composition of Example 1 had a failure loss of 180 psi whereas the composition without the phenyl phosphinic acid additive failed at 25 to 50 psi.

A fluid composed of the base oil from Example 1 but containing 0.1 percent by weight of phenyl phosphinic acid as the lubricity additive was run in slow speed four ball test using M-50 steel for the ball and discs. This fluid had a lower boundary friction than the unblended oil from 200 F. to 500 F. and from 600 to 700 F. At no temperature from room temperature to 700 F. did the friction of the blend significantly exceed that of the base stock.

It will be appreciated that the composition of the invention, in addition to the polyphenyl thioether base fluid and the organic phosphinic acid additive, may also contain other additives, such as oxidation inhibitors, rust and corrosion inhibitors, antifoaming agents, detergents, viscosity index improvers such as polymeric materials for example, polyacrylate alkyl esters, polymethacrylate alkyl esters, polyoxyalkylene compounds, polyurethanes and the like. Such additives are usually employed in amounts as low as 10 parts per million for antifoaming agent to as much as 15 parts by weight of the total compositions for viscosity index improvers.

wherein R is a phenyl group or a substituted phenyl group, R is a phenylene group or substituted phenylene group, in which the substituents on said phenyl and phenylene groups are halogen, alkyl or alkoxy containing from one to four carbon atoms, n is an integer of from one to six, Y is sulfur or oxygen provided that at least one of the groups represented by Y is sulfur, and mixtures of such thioethers and from about 0.05 to about 2.0 percent by weight of an organic phosphinic acid of the formula wherein R" is an aryl group containing from six to sixteen carbon atoms, a halogen substituted aryl group containing from six to sixteen carbon atoms, an alkyl substituted aryl group containing from six to 16 carbon atoms or an alkyl group containing one to 12 carbon atoms.

2. A composition of claim 1 wherein said organic phosphinic acid is present in amounts of from about 0.075 to about 0.2 percent by weight.

3. A composition of claim 1 wherein said organic phosphinic acid is phenyl phosphinic acid.

4. A composition of claim 2 wherein said organic phosphinic acid is phenyl phosphinic acid.

5. A composition of claim 1 where n is from one to three. 

2. A composition of claim 1 wherein said organic phosphinic acid is present in amounts of from about 0.075 to about 0.2 percent by weight.
 3. A composition of claim 1 wherein said organic phosphinic acid is phenyl phosphinic acid.
 4. A composition of claim 2 wherein said organic phosphinic acid is phenyl phosphinic acid.
 5. A composition of claim 1 where n is from one to three. 